BACKGROUND Multiple sclerosis(MS)is known to affect many sensory systems,yet most auditory research in MS has focused on the afferent pathways,with relatively few studies examining efferent function.The brainstem is a...BACKGROUND Multiple sclerosis(MS)is known to affect many sensory systems,yet most auditory research in MS has focused on the afferent pathways,with relatively few studies examining efferent function.The brainstem is a common site for MS plaques,and the medial olivocochlear(MOC)system is located in the superior olivary complex(SOC)of the brainstem.The cochlear nuclei are also involved in the MOC reflex arc.Additionally,the temporal cortex can modulate the SOC and cochlear nucleus,so lesions in the brainstem or temporal cortex may affect the MOC reflex in MS.AIM To investigate efferent auditory system activity in patients with multiple sclerosis via the MOC reflex.METHODS The study included 50 patients with MS and 50 healthy controls.Patients with MS were divided into three subgroups according to cranial magnetic resonance imaging findings:Patients with brainstem lesions(Group 1,n=20);patients with temporal cortex lesions without brainstem involvement(Group 2,n=20);and patients without any lesions in the brainstem or temporal cortex(Group 3,n=10).Tympanometry,acoustic stapedial reflex thresholds,pure-tone audiometry,and transientevoked otoacoustic emission(TEOAE)tests(with and without contralateral noise)were performed for all participants.RESULTS There was no significant difference in pure-tone hearing thresholds or baseline TEOAE amplitudes between the MS and control groups,indicating normal cochlear function in patients with MS;however,MOC reflex suppression was significantly reduced in patients with MS compared to controls(P=0.021).In particular,Group 1(MS with brainstem lesions)showed the lowest mean suppression values,which was significantly lower than that of Group 2 and the control group(P=0.002).By contrast,Group 2 and Group 3 did not significantly differ from controls.Additionally,patients with MS exhibited a sex difference in MOC function:Male patients had significantly lower suppression compared to female patients both within Group 1 and in the MS group as a whole.CONCLUSION The findings indicate that the efferent auditory system(specifically the MOC reflex)is affected by MS.MOC reflex activity was most significantly decreased in patients with MS with brainstem lesions,while temporal cortex lesions alone did not appear to notably impair the MOC reflex.Diminished MOC activity may underlie various auditory difficulties in patients with MS(e.g.,hearing in noise),and loss of efferent suppression could contribute to symptoms such as hyperacusis or tinnitus in this population.Further studies are needed to better understand the relationship between MOC dysfunction and auditory symptoms in MS,as well as the potential diagnostic value of MOC testing in MS.展开更多
Background:The activation of the medial olivocochlear reflex reduces the cochlear gain,which is manifested perceptually as decreased auditory sensitivity.However,it has remained unclear whether the extent of this supp...Background:The activation of the medial olivocochlear reflex reduces the cochlear gain,which is manifested perceptually as decreased auditory sensitivity.However,it has remained unclear whether the extent of this suppression varies according to the cochlear region involved.Here we aims to assess the magnitude of contralateral efferent suppression across human cochlea,at low levels,and its impact on hearing sensitivity.Methods:Assuming that acoustic stimulation activates the contralateral medial olivocochlear reflex,we evaluated the magnitude of the suppressive effect as a function of frequency in 17 subjects with normal hearing.Absolute thresholds were measured for bursts tones of various durations(10,100,and 500 ms)and frequencies(250,500,1000,4000,and 8000 Hz)in the presence or absence of contralateral white noise at 60 d B SPL.Results:We found that contralateral noise raised the absolute threshold for the burst tones evaluated.The effect was greater at lower than higher frequencies(3.85 d B at 250 Hz vs.2.22 d B at 8000 Hz).Conclusions:Our findings suggest that in humans,the magnitude of this suppression varies according to the cochlear region stimulated,with a greater effect towards the apex(lower frequencies)than the base(higher frequencies)of the cochlea.展开更多
目的:探讨猫上橄榄复合体各个核团内橄榄耳蜗神经元的分布和形态。方法:将8只成年猫随机分成两组,实验组5只,于左侧耳蜗内注射霍乱毒素B亚单位(cholera toxin B subunit,CTB),右侧耳蜗注射荧光金(fluoro-gold,FG);对照组3只,于双侧耳蜗...目的:探讨猫上橄榄复合体各个核团内橄榄耳蜗神经元的分布和形态。方法:将8只成年猫随机分成两组,实验组5只,于左侧耳蜗内注射霍乱毒素B亚单位(cholera toxin B subunit,CTB),右侧耳蜗注射荧光金(fluoro-gold,FG);对照组3只,于双侧耳蜗注射生理盐水。取脑干组织切片,经免疫组化ABC方法和DAB显色后观察被标记的橄榄耳蜗神经元。结果:实验组猫橄榄耳蜗神经元总数为2518个,其中外侧橄榄耳蜗(lateral olivocochlear,LOC)神经元1738个,占69.0%,主要分布于脑桥中部,以同侧投射占优势。内侧橄榄耳蜗(medial olivocochlear,MOC)神经元780个(31.0%),主要位于背内侧橄榄旁核(dorsomedial periolivary nucleus,DMPO)、内侧斜方体核(medial nucleus of the trapezoid body,MNTB)以及腹侧斜方体核(ventral nucleus of the trapezoid body,VNTB),在脑桥嘴侧分布密集,其发出的纤维以对侧投射占优势。结论:猫的橄榄耳蜗神经元分布LOC神经元向同侧投射为主;而MOC神经元则为对侧投射优势,且MOC神经元分布较LOC神经元更靠近脑桥嘴侧。展开更多
Previous research has demonstrated that the amplitude of evoked emissions decreases in human sub-jects when the contralateral ear is stimulated by noise. The medial olivocochlear bundle (MOCB) is be-lieved to control ...Previous research has demonstrated that the amplitude of evoked emissions decreases in human sub-jects when the contralateral ear is stimulated by noise. The medial olivocochlear bundle (MOCB) is be-lieved to control this phenomenon. Recent research has examined this effect in individuals with auditory pro-cessing disorders (APD), specifically with difficulty understanding speech in noise. Results showed tran-sient evoked otoacoustic emissions (TEOAEs) were not affected by contralateral stimulation in these sub-jects. Much clinical research has measured the function of the MOCB through TEOAEs.This study will use an alternative technique, distortion product otoacoustic emissions (DPOAEs), to examine this phenomenon and evaluate the function of the MOCB. DPOAEs of individuals in a control group with normal hearing and no significant auditory processing difficulties were compared to the DPOAEs of children with signifi-cant auditory processing difficulties.Results showed that the suppression effect was observed in the control group at 2 kHz with 3 kHz of narrowband noise. For the auditory processing disorders group, no significant suppression was observed.Overall, DPOAEs showed suppression with contralateral noise, while the APD group levels increased overall.These results provide further evidence that the MOCB may have reduced function in children with APD.展开更多
文摘BACKGROUND Multiple sclerosis(MS)is known to affect many sensory systems,yet most auditory research in MS has focused on the afferent pathways,with relatively few studies examining efferent function.The brainstem is a common site for MS plaques,and the medial olivocochlear(MOC)system is located in the superior olivary complex(SOC)of the brainstem.The cochlear nuclei are also involved in the MOC reflex arc.Additionally,the temporal cortex can modulate the SOC and cochlear nucleus,so lesions in the brainstem or temporal cortex may affect the MOC reflex in MS.AIM To investigate efferent auditory system activity in patients with multiple sclerosis via the MOC reflex.METHODS The study included 50 patients with MS and 50 healthy controls.Patients with MS were divided into three subgroups according to cranial magnetic resonance imaging findings:Patients with brainstem lesions(Group 1,n=20);patients with temporal cortex lesions without brainstem involvement(Group 2,n=20);and patients without any lesions in the brainstem or temporal cortex(Group 3,n=10).Tympanometry,acoustic stapedial reflex thresholds,pure-tone audiometry,and transientevoked otoacoustic emission(TEOAE)tests(with and without contralateral noise)were performed for all participants.RESULTS There was no significant difference in pure-tone hearing thresholds or baseline TEOAE amplitudes between the MS and control groups,indicating normal cochlear function in patients with MS;however,MOC reflex suppression was significantly reduced in patients with MS compared to controls(P=0.021).In particular,Group 1(MS with brainstem lesions)showed the lowest mean suppression values,which was significantly lower than that of Group 2 and the control group(P=0.002).By contrast,Group 2 and Group 3 did not significantly differ from controls.Additionally,patients with MS exhibited a sex difference in MOC function:Male patients had significantly lower suppression compared to female patients both within Group 1 and in the MS group as a whole.CONCLUSION The findings indicate that the efferent auditory system(specifically the MOC reflex)is affected by MS.MOC reflex activity was most significantly decreased in patients with MS with brainstem lesions,while temporal cortex lesions alone did not appear to notably impair the MOC reflex.Diminished MOC activity may underlie various auditory difficulties in patients with MS(e.g.,hearing in noise),and loss of efferent suppression could contribute to symptoms such as hyperacusis or tinnitus in this population.Further studies are needed to better understand the relationship between MOC dysfunction and auditory symptoms in MS,as well as the potential diagnostic value of MOC testing in MS.
基金Work supported by a grant of the University of Chile(UI-10/16)to EA。
文摘Background:The activation of the medial olivocochlear reflex reduces the cochlear gain,which is manifested perceptually as decreased auditory sensitivity.However,it has remained unclear whether the extent of this suppression varies according to the cochlear region involved.Here we aims to assess the magnitude of contralateral efferent suppression across human cochlea,at low levels,and its impact on hearing sensitivity.Methods:Assuming that acoustic stimulation activates the contralateral medial olivocochlear reflex,we evaluated the magnitude of the suppressive effect as a function of frequency in 17 subjects with normal hearing.Absolute thresholds were measured for bursts tones of various durations(10,100,and 500 ms)and frequencies(250,500,1000,4000,and 8000 Hz)in the presence or absence of contralateral white noise at 60 d B SPL.Results:We found that contralateral noise raised the absolute threshold for the burst tones evaluated.The effect was greater at lower than higher frequencies(3.85 d B at 250 Hz vs.2.22 d B at 8000 Hz).Conclusions:Our findings suggest that in humans,the magnitude of this suppression varies according to the cochlear region stimulated,with a greater effect towards the apex(lower frequencies)than the base(higher frequencies)of the cochlea.
文摘目的:探讨猫上橄榄复合体各个核团内橄榄耳蜗神经元的分布和形态。方法:将8只成年猫随机分成两组,实验组5只,于左侧耳蜗内注射霍乱毒素B亚单位(cholera toxin B subunit,CTB),右侧耳蜗注射荧光金(fluoro-gold,FG);对照组3只,于双侧耳蜗注射生理盐水。取脑干组织切片,经免疫组化ABC方法和DAB显色后观察被标记的橄榄耳蜗神经元。结果:实验组猫橄榄耳蜗神经元总数为2518个,其中外侧橄榄耳蜗(lateral olivocochlear,LOC)神经元1738个,占69.0%,主要分布于脑桥中部,以同侧投射占优势。内侧橄榄耳蜗(medial olivocochlear,MOC)神经元780个(31.0%),主要位于背内侧橄榄旁核(dorsomedial periolivary nucleus,DMPO)、内侧斜方体核(medial nucleus of the trapezoid body,MNTB)以及腹侧斜方体核(ventral nucleus of the trapezoid body,VNTB),在脑桥嘴侧分布密集,其发出的纤维以对侧投射占优势。结论:猫的橄榄耳蜗神经元分布LOC神经元向同侧投射为主;而MOC神经元则为对侧投射优势,且MOC神经元分布较LOC神经元更靠近脑桥嘴侧。
文摘Previous research has demonstrated that the amplitude of evoked emissions decreases in human sub-jects when the contralateral ear is stimulated by noise. The medial olivocochlear bundle (MOCB) is be-lieved to control this phenomenon. Recent research has examined this effect in individuals with auditory pro-cessing disorders (APD), specifically with difficulty understanding speech in noise. Results showed tran-sient evoked otoacoustic emissions (TEOAEs) were not affected by contralateral stimulation in these sub-jects. Much clinical research has measured the function of the MOCB through TEOAEs.This study will use an alternative technique, distortion product otoacoustic emissions (DPOAEs), to examine this phenomenon and evaluate the function of the MOCB. DPOAEs of individuals in a control group with normal hearing and no significant auditory processing difficulties were compared to the DPOAEs of children with signifi-cant auditory processing difficulties.Results showed that the suppression effect was observed in the control group at 2 kHz with 3 kHz of narrowband noise. For the auditory processing disorders group, no significant suppression was observed.Overall, DPOAEs showed suppression with contralateral noise, while the APD group levels increased overall.These results provide further evidence that the MOCB may have reduced function in children with APD.
